부산대학교 도서관

Hypoxia or anoxia occurs every summer in the inner Ariake Sea and Isahaya Bay now. Dome-shaped water named “cold-dome water” formed in the middle of Ariake Sea has strong relationship with the generation of hypoxia/anoxia in two areas. Cold-dome water with lower temperature than surrounding water intrudes into bottom of inner Ariake Sea and Isahaya Bay at neap tides and intensifies density stratification. The intruded water then generates hypoxia/anoxia there. Therefore, DO concentration in cold-dome water before intrusion is an important factor that affects duration and severity of hypoxia as an initial DO concentration. The present study evaluated DO dynamics in the middle of Ariake Sea by moored continuous field observation and numerical simulation using ecosystem model. The field observation confirmed that the DO concentration decreased from neap tide to spring tide, which differed from the spring-neap variation in DO concentration in the inner Ariake Sea and Isahaya Bay. Numerical simulation reproduced such decrease in DO concentration in the middle of Ariake Sea. DO budget analysis revealed that the decrease of DO supply due to horizontal advection caused the decrease in DO concentration in the cold-dome water. Change in DO supply associated with spring-neap variation of estuarine circulation and the transport of low DO water from Isahaya Bay to the middle of Ariake Sea along Shimabara Peninsula were reasons for the decrease in the advective DO supply.